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Group 31 AGM Starting Battery: 1150 MCA for Bigger Engines
Short answer: A Group 31 AGM starting battery like the Pro-Guide 31MX1150 is a sealed 12V marine cranking battery rated at 1150 marine cranking amps (MCA), 925 cold cranking amps (CCA) and 200 minutes of reserve capacity in a Group 31 case (13 x 6 13/16 x 8 7/8 in, 60 lb). It is the most powerful battery in the Pro-Guide AGM starting line, built for engines that need more than 935 MCA, cold-weather launches and boats that carry heavy electrical loads.
When a smaller starting battery leaves you listening to a slow, laboring starter, the fix is usually more cranking amps and more reserve, not a new starter. This guide explains what 1150 MCA and 925 CCA mean in practice, how to size a Group 31 starting battery for larger outboards, sterndrives and twin-engine boats, how to use reserve capacity wisely, and how to charge and install an AGM for a long service life.
Key Takeaways
- Top of the line: 1150 MCA and 925 CCA, the highest cranking ratings in the Pro-Guide AGM starting range.
- Biggest reserve: 200 minutes at 25A to carry essential loads if the charging system fails or you run gear at anchor.
- Higher charge acceptance rating: 10A standard, 20A maximum charge current.
- Sealed AGM: no watering, no free liquid acid, built for vibration and spray.
- Proven by owners: 4.88 out of 5 stars across 17 reviews, with an 18-month free replacement warranty.
What Is a Group 31 AGM Starting Battery?
"Group 31" is a case-size standard from the Battery Council International (BCI). It is the longest of the three common marine sizes (24, 27 and 31), and the extra length leaves room for more plate area. In a starting battery, more plate area means more current available to the starter and more reserve capacity.
Group 31 batteries are common on larger center consoles, offshore boats, cruisers, sterndrive runabouts and boats with twin engines, as well as in heavy-duty trucks and equipment. If your boat already has a Group 31 tray, it was likely sized for an engine and electrical system that benefit from the extra power.
The Pro-Guide 31MX1150 is a dedicated AGM (absorbent glass mat) starting battery. The electrolyte is held in glass mats between tightly packed plates, so the battery is sealed, spill-resistant and maintenance-free. Pro-Guide designed its AGM starting line for reliable engine starts in demanding marine environments, and the 31MX1150 carries the line's highest ratings.
Pro-Guide 31MX1150 Specifications
| Model / SKU | Pro-Guide 31MX1150 (PGM31MX1150) |
| Type | AGM marine starting battery |
| Group size | BCI Group 31 |
| Voltage | 12V |
| Marine cranking amps (MCA) | 1150 |
| Cold cranking amps (CCA) | 925 |
| Reserve capacity | 200 minutes at 25A |
| Charge current (standard / max) | 10A / 20A |
| Charging temperature | 0°F to 122°F |
| Discharge temperature | -4°F to 140°F |
| Terminals | 1 SAE post, 1 stud terminal |
| Dimensions (L x W x H) | 13 x 6 13/16 x 8 7/8 in (330 x 173 x 225 mm) |
| Weight | 60 lb (27 kg) |
| Warranty | 18-month free replacement |
Want the full numbers? Download the 31MX1150 data sheet (PDF).
The 31MX1150 label shows the ratings that set it apart: 1150 MCA, 925 CCA and 200 minutes of reserve capacity.
What Do 1150 MCA and 925 CCA Mean?
Cranking ratings tell you how much current a battery can deliver to your starter, and at what temperature.
| Rating | Test conditions | 31MX1150 |
| Marine cranking amps (MCA) | 30 seconds at 32°F, holding at least 7.2V | 1150 |
| Cold cranking amps (CCA) | 30 seconds at 0°F, holding at least 7.2V | 925 |
| Reserve capacity (RC) | Minutes of 25A output when fully charged | 200 |
Higher cranking amps help in three situations. First, larger engines with high compression and big starters draw more current to turn over. Second, cold starts thicken engine oil and weaken any battery, which is why the 925 CCA rating matters if you launch in spring, fall or cold climates. Third, aging batteries lose cranking ability over time, so starting with a higher rating gives you more margin as the battery gets older.
For comparison, the Group 24 and Group 27 Pro-Guide AGM starting batteries are rated 935 MCA and 750 CCA. The 31MX1150 adds 215 MCA and 175 CCA on top of that.
Do You Need a Group 31 Starting Battery?
Start with your engine's owner's manual. Outboard, sterndrive and inboard manufacturers list a minimum battery rating, usually in MCA, CCA or both. Then work through these questions:
- Does your engine require more than 935 MCA or 750 CCA? If yes, a Group 24 or 27 at that rating won't meet spec. The 31MX1150 covers engines that call for up to 1150 MCA or 925 CCA.
- Do you start more than one engine from one bank? On some twin-engine setups, or when a kicker motor shares the bank, the extra capacity helps. Follow your engine and rigging manufacturer's wiring guidance.
- Do you launch in cold weather? Compare CCA, not just MCA.
- Do you run a lot of gear on the starting bank? Windlasses, stereos, lighting and pumps all draw from the same battery. More reserve capacity protects your ability to start.
- Will it fit? The 31MX1150 measures 13 x 6 13/16 x 8 7/8 in and weighs 60 lb. Confirm length, height and terminal clearance before ordering.
If your engine's minimum is 935 MCA or less and you have a smaller tray, the 24MX935 or 27MX935 may be all you need.
Reserve Capacity: How Long Will 200 Minutes Last?
Reserve capacity is the best guide to how long a starting battery can carry loads with the engine off. At 25A, the 31MX1150 lasts about 200 minutes, which works out to roughly 83 amp-hours delivered at that rate. To keep enough charge to restart and to protect a lead-acid battery, plan on using only about half, or around 42Ah.
| Engine-off load | Typical draw | Rough estimate using about half the reserve |
| Chartplotter or VHF on standby | About 2A | About 21 hours |
| Nav and anchor lights, graph, bilge pump cycling | About 5A | About 8 hours |
| Stereo, cabin lights and fridge or livewell together | About 10A | About 4 hours |
These are conservative, rough estimates; real runtime depends on temperature, battery age and how the loads cycle. One Sea Ray owner reported installing two Pro-Guide Group 31 AGMs wired in parallel, using them to power accessories all day and still starting the boat for the ride home without issue. If your engine-off loads are large or run for long stretches, a separate house battery is still the best design. See Should You Run a Separate Battery for Your Boat Electronics?
AGM vs. Flooded vs. Lithium Group 31 Starting Batteries
| Factor | AGM (Pro-Guide 31MX1150) | Typical flooded Group 31 | Typical lithium starting |
| Maintenance | Sealed; no watering | Regular water checks | None |
| Spill risk | Electrolyte held in glass mats | Liquid acid can spill if tipped | No liquid electrolyte |
| Vibration resistance | Generally good | Generally lower | Generally good |
| Cold cranking | 925 CCA at 0°F | Varies by model | Can be limited in freezing temperatures |
| Charging system | Works with existing systems; AGM charger mode | Works with existing systems | Check compatibility first |
| Weight | 60 lb | Often similar or heavier | Much lighter |
| Upfront cost | Mid | Lowest | Highest |
On bigger boats that pound offshore, the sealed, vibration-resistant AGM design is a strong fit, and it works with the engine's existing alternator and a standard AGM-capable charger. Pro-Guide describes its AGM starting line as offering better performance and longer life than traditional flooded options. Lithium can save a lot of weight, but it costs more and may need charging-system changes. To compare, browse starting lithium batteries.
What Is the 31MX1150 Best For?
- Larger outboards and sterndrives: engines whose manual calls for more than 935 MCA, up to 1150 MCA or 925 CCA.
- Offshore center consoles and cruisers: boats with Group 31 trays, heavy electrical loads and long days away from the dock.
- Cold-weather boating: early-season and late-season anglers who need the extra CCA.
- Pleasure boats that run gear at anchor: 200 minutes of reserve gives more cushion for stereos, lights and pumps before you need to restart.
- Dual-battery systems: a dedicated cranking battery alongside deep cycle trolling or house batteries. See One Pack or Three? Choosing the Right Trolling Motor Battery Setup.
Owners rate the 31MX1150 4.88 out of 5 across 17 reviews, describing it as very dependable and praising Pro-Guide's fast shipping and service.
Top view of the 31MX1150: integrated carry handle for the 60 lb case, covered terminals and the rating label.
How to Charge a Group 31 AGM Starting Battery
The engine's alternator recharges the 31MX1150 while you run. Off the water, a charger keeps it ready. Follow these guidelines:
- Use an AGM charging profile. AGM batteries charge best on an AGM-specific setting. Avoid flooded-only or lithium profiles.
- Stay within the rating. Pro-Guide rates the 31MX1150 for 10A standard and 20A maximum charge current. A 12V 10A 1-Bank Battery Charger matches the standard rate. For a starting battery plus house or trolling batteries, a 12V 10A 2-Bank Battery Charger charges both banks independently.
- Charge between 0°F and 122°F. That is the rated charging range; the battery can discharge from -4°F to 140°F.
- Recharge after drawing down the reserve. Lead-acid batteries, including AGM, can sulfate if left partially discharged.
- Maintain it in storage. Keep it on a smart maintainer over the off-season, or charge it fully, disconnect it and top it up periodically.
Installation Tips for a 60 lb Battery
Lift it safely
At 60 lb, the 31MX1150 is the heaviest battery in the Pro-Guide AGM starting line. Use the built-in carry handle, lift with your legs and get help if you are reaching down into a deep compartment.
Secure it with the right tray or box
A loose Group 31 battery can do real damage in rough water. Strap it into a NOCO Group 31 Battery Tray or a Group 24-31 Plastic Battery Box. For extra protection against pounding, add a battery shock absorber.
Use the right terminal
The 31MX1150 offers an SAE post and a stud terminal. Many larger boats use ring terminals on studs for heavy cables; tighten them firmly and keep the positive covered.
Fight corrosion
Treat terminals with battery corrosion preventative spray, especially in salt water.
Carry backup power
A 12V 1000A jump starter is cheap insurance on any boat.
For more seasonal care, read our marine battery maintenance guide.
31MX1150 vs. 27MX935: Which Should You Choose?
| Spec | 27MX935 | 31MX1150 |
| Group size | 27 | 31 |
| MCA / CCA | 935 / 750 | 1150 / 925 |
| Reserve capacity | 175 minutes | 200 minutes |
| Max charge current | 15A | 20A |
| Length | 12 1/16 in | 13 in |
| Weight | 50 lb | 60 lb |
Choose the 27MX935 if your engine calls for 935 MCA or less and you have a Group 27 tray. Choose the 31MX1150 if your engine needs more cranking power, you boat in the cold, or you want the most reserve capacity in the Pro-Guide AGM starting line.
Frequently Asked Questions
What is the most powerful Pro-Guide AGM starting battery?
The Pro-Guide 31MX1150 is the most powerful in the line, rated 1150 MCA, 925 CCA and 200 minutes of reserve capacity in a Group 31 case.
How many cranking amps does a Group 31 starting battery have?
It varies by brand and model. The Pro-Guide 31MX1150 is rated 1150 marine cranking amps and 925 cold cranking amps.
When should I choose a Group 31 over a Group 27 starting battery?
Choose a Group 31 when your engine needs more than 935 MCA, when you launch in cold weather, or when you want more reserve. The Pro-Guide 31MX1150 adds 215 MCA and 25 minutes of reserve over the 27MX935.
Can I wire two Group 31 AGM batteries in parallel?
Yes, two identical 12V batteries in parallel stay at 12V and combine their capacity. One Sea Ray owner runs two Pro-Guide 31MX1150 batteries in parallel for accessories and starting.
Can the 31MX1150 run a trolling motor?
It is not designed for that. The Pro-Guide 31MX1150 is a starting battery; use a dedicated deep cycle battery for a trolling motor.
What charger should I use for a Group 31 AGM starting battery?
Use a charger with an AGM setting. The Pro-Guide 31MX1150 is rated for 10A standard and 20A maximum charge current.
How much does the 31MX1150 weigh?
The Pro-Guide 31MX1150 weighs 60 lb (27 kg) and measures 13 x 6 13/16 x 8 7/8 in.
What warranty does the 31MX1150 have?
The Pro-Guide 31MX1150 includes an 18-month free replacement warranty.
Get Maximum AGM Cranking Power
If your engine needs more than 935 MCA, you boat in cold weather, or you simply want the most cranking power and reserve you can fit in a Group 31 tray, the Pro-Guide 31MX1150 is the battery to choose. It is sealed, maintenance-free, rated 4.88 out of 5 by owners and backed by an 18-month free replacement warranty.
Need help matching a battery to your engine? Call our team at 1-800-827-3232 or browse all AGM batteries and marine batteries.
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